Apparatus for saturating webs of felted fibres



July 25, 1961 w. N. STICKEL 2,993,470

APPARATUS FOR SATURATING WEBS 0F FELTED FIBRES Filed Aug. 13, 1958 IIllllllIllllllllllllllllll I INVENTOR. WESLEY N. STICKEL QTTOENEYS United States Patent 2,993,470 APPARATUS FOR 'SATURATING WEBS 0F FELTED FIBRES Wesley N. Stickel, Westfield, Mass., assignor to Texon, Inc, South Hadley Falls, Mass., a corporation of Massachusetts Filed Aug. 13, 1958, Ser. No. 754,740 6 Claims. (Cl. 118-407) This invention relates to the production of saturated webs or sheets of felted fibres and has particular reference to an improved apparatus for applying the saturant to such webs or sheets.

It is common practice to form a wet web of fibrous stock, as from a pulp solution, partially dry the wet web so that it is self-sustaining, and then impregnate the wet web with a saturant, such as liquid rubber latex. The saturant may include the latex compounded with various additives such as stabilizers, anti-oxidants, sensitizers, etc. The apparatus commonly used for applying the saturant to the wet web comprises a container for the saturant, a rotatably mounted screen roll having the lower portion of its cylindrical surface immersed in the saturant in the container, and an endless screen belt forming a conveyor on which the wet web is carried through the saturant in the container while held against the lower portion of the cylindrical surface of the screen roll. Apparatus of this type is disclosed in Novak Patents Nos. 1,966,458 and 2,078,272, dated iuly 17, 1934 and April 27, 1937, respectively. A characteristic of this prior apparatus is that it includes synchronously moving foraminated surfaces between which the web passes as it moves through the saturant in the container, the foraminated surface of the screen roll serving to submerge the web in the saturant while allowing teh saturant to contact the upper surface of the web which contacts this roll.

The above described prior apparatus has several 'disadvantages, an important one of which is that the holes in the foraminous surface of the screen roll tend to become plugged with the saturant, which requires rather frequent cleaning of this roll. In addition, the upper surface of the impregnated web, when treated in such an apparatus, has wire marks or similar marks left on this surface by the foraminated cylindrical surface of the roll.

The difficulties above-referred to have been evident particularly when impregnating a cellulosic web with latex. Under these circumstances, and it is believed, due in part at least to air emanating from the Web when it was pressed against the screen roll of the prior art structure causing foaming inside the screen roll, there has been a coagulation of rubber-like material, which tended not only to plug the perforations in the screen of the roll surface, but also tended to deposit particles of rubberlike material both on the outside of the screen roll, causing depressions in the surface of the web in contact therewith, and also to deposit particles of rubber or rubberlike material directly on the impregnated web. This caused substantial losses due to damage to the final product. In attempting to avoid these losses, frequent cleaning of the roll was resorted to, which substantially increased the labor cost of carrying on the process as well as introducing substantial shutdown times for the apparatus for cleaning and/ or changing the rolls to replace them by cleaned rolls.

The present invention provides an apparatus which practically overcomes these difficulties and provides apparatus which will not only operate with a minimum of shutdown time for cleaning and other repairs as well as at a minimum labor cost, but also provides for the making of a saturated web having a smooth surface in contact with the imperforate-surfaced roll used in accordice dance with the present invention, in lieu of a web having the wire marks of the screen roll of the prior art.

An apparatus made according to the invention comprises a saturant container, and a roll mounted above the container for rotation about a generally horizontal axis, this roll having a smooth imperforate cylindrical surface which at its lower portion is located in the container so that it is immersed in the saturant. An endless screen extends through this container below the roll and forms a porous supporting surface for the web. Means are provided for moving this supporting surface under tension to carry the web through the saturant while pressing the web against the lower portion of the imperforate cylindrical surface of the roll, the latter being rotated to move its lower portion in the direction of movement of the supporting surface of the endless screen. A scraper engages the imperforate cylindrical surface of the roll to remove any material adhering to this surface.

I have discovered that despite that fact that the imperforate surface of the roll blocks off the free liquid saturant from the upper surface of the web where it contacts this roll, the apparatus of my invention provides a better impregnation of the web than is obtained with the prior apparatus. The pressing action of the imperforate cylindrical surface in squeezing the web between it and the screen makes it possible to extract a greater amount of moisture from the web before it reaches the primary impregnating zone, in one form of the invention, which, in turn, enables faster drying of the impregnated web. Moreover, in another form of the invention, the greater pressing action of the imperforate cylindrical surface forces the saturant downwardly through the web in such a manner as to provide a more uniform distribution of the saturant in the web. By using a roll which is imperforate and providing the scraper for removing any material tending to adhere to the smooth cylindrical surface of the roll, the usual mold or wire marks are eliminated from the upper surface of the web; and, of course, there is no need to shut down the apparatus due to clogging of the roll. Finally, the new apparatus eliminates the problem of having air trapped in the web, which tends to cause delamination after drying. The greater pressures allowed between the smooth imperforate roll and the underlying carrier screen act to force any air downwardly out of the web as the saturant is forced through the web in one form of the invention.

For a better understanding of the invention, reference may be had to the accompanying drawing, in which:

FIG. 1 is a diagrammatic side elevational view, partly in cross section, of a preferred form of the new apparatus;

FIG. 2 is a detailed perspective view of the imperforate roll shown in FIG. 1; and

FIG. 3 is a view similar to FIG. 1 but showing a modified form of the apparatus.

Referring to FIG. 1, the apparatus there shown comprises an endless screen belt 3 which is trained around rolls 4, 5, 6 and 7. The rolls 4 and 5 are mounted on and driven by shafts 4a and 5a, respectively, so that the upper section 30 of the screen belt moves to the left as viewed in FIG. 1. This upper section 3:: forms a porous supporting surface of the wet web W which comes from the apparatus (not shown) forming the wet web.

The upper section 3a of the screen belt is deflected downwardly intermediate its ends by an imperforate roll 9. The latter, as best shown in FIG. 2, has a smooth imperforate cylindrical surface 9a and is preferably provided with closed ends 9b and 9c. The roll 9 has shafts 10 at its opposite ends, these shafts serving to mount the roll for rotation about a generally horizontal axis extending transversely of the screen belt 3. The shafts 10 also serve as a means for driving the roll 9 about its axis in the direction of the arrow in FIG. 1.

Below the imperforate roll 9 is a saturant container 12 filled with a liquid saturant 13. The lower portion of the imperforate cylindrical surface 9a of the roll is immersed in the saturant 13.

A scraper 15, such as a doctor blade, is mounted above the imperforate roll 9, the scraper blade contacting the cylindrical surface 9a along the length of the roll. Above the scraper 15 is a saturant delivery means which, as shown, is in the form of a trough 16 to which a saturant 17 is supplied from any suitable source (not shown). The lower edge of the trough 16 is so located that the saturant is supplied continuously on the underlying cylindrical surface of the roll 9 in the region of the scraper 15, so that this saturant is delivered to the outlet side of the nip between the roll 9 and the underlying porous supporting surface of the web-supporting reach 3a of the screen 3.

In the operation of the apparatus shown in FIG. 1', the driven rolls 4 and 5 serve as a means for moving the porous supporting surface 3a under tension to carry the web W through the saturant 13 while pressing the web against the lower portion of the imperforate cylindrical surface of the roll 9. The roll 9 is mounted for rotation about a generally horizontal axis, namely, the axis of the shafts 10 and is rotated so that the lower portion of its cylindrical surface is movable in the direction of movement of the underlying supporting surface of the wire screen 3 and at the same speed. The screen 3 is arranged about the driven rolls 4 and 5 so as to exert a considerable pressure upon the web W, so as to squeeze out water out of the web in a downward direction during the portion of the path of the web in which it is squeezed between the web-supporting reach 3a of the wire screen 3 and the roll 9. When, as shown in FIG. land in greater detail in FIG. 3, there is a portion of the saturant adjacent to the nip where the web W approaches contact with the roll 9 and above the web, the liquid body of the saturant tends to be squeezed into the web and in turn tends to force water out of the web through the perforated screen 3. The water content of the web is also pressed out of it and in a downward direction away from the imperforate roll between the lower portion of the roll and the screen, while the web W is squeezed therebetween. As the web W and the screen 3 pass away from contact with the roll 9 at the nip on the left of the roll as seen in FIG. 1, the web is relieved of the pressure to which it had been subjected; and due to the porous and somewhat elastic character thereof, acts at this time rapidly to absorb the liquid saturant, which is maintained as a pool above the web due to the supplying of the liquid saturant from the trough 16 disposed above and generally parallel to the axis of the roll 9 as shown.

As the imperforate roll 9 rotates, the scraper removes any material adhering to the smooth cylindrical surface, such as saturant or fibers, so that the surface of the roll moving into contact with the web W is perfectly smooth, thereby avoiding marks on the upper surface of the web.

The modified form of the apparatus shown in FIG. 3 is similar to that illustrated in FIG. 1, except that in FIG. 3 the guide roll 6 for conveyor screen 3 is located in a more elevated position above container 12, and the web W is fed into contact with screen 3 over a roll 18 located above the roll 6. In this way, a fairly deep recess is formed at the entrance angle between web W and roll 9, this recess serving to pocket a body of saturant delivered from the overlying supply trough 16a. As shown in FIG. 3, the trough 16a delivers saturant from both sides of the trough, so that the saturant is delivered upon the roll 9 in the region of scraper 15 and also to the inlet side of the nip between roll 9 and the conveyor screen 3.

In the form of the invention shown in FIG. 3, which is for many purposes a preferred form of the invention, not only are the web W and the active or web-supporting reach 3:: of the screen introduced into contact with the roll 9 from above, so as to be in contact with the roll for a larger portion of its periphery than the form shown in FIG. 1, but also the trough 16a delivers saturant to both sides of the roll, so that a pool is established and maintained leading into the nip at which the web W is brought into contact with the roll 9 and another pool is established and maintained in the nip where the web is moved out of contact with the roll as seen at the left thereof. The operation of the form of the invention shown in FIG. 3 is otherwise essentially similar to that described with respect to the form of the invention shown in FIG. 1.

While there is herein shown and described but two forms of the invention, it is recognized that the principles herein disclosed are capable of further modifications which will suggest themselves to those skilled in the art from the foregoing description and drawings. It is intended that all such modifications which come within the scope of the appended claims are to be considered as a part of the present invention.

I claim:

1. Apparatus for saturating a wet web of felted fibres, which comprises a saturant container adapted to contain a saturant up to a predetermined level, a roll having a substantially cylindrical imperforate surface mounted above said container for rotation about a generally horizontal axis, said roll being so mounted that the lower portion of the imperforate cylindrical surface thereof extends into said container to a point below said predetermined level, so that said imperforate surface is adapted to be immersed in the saturant in said container; an endless screen having a web-supporting reach extending through said container below said roll and including a part approaching said roll, a part below and serving to confine said web under pressure between the surface of said screen and the imperforate surface of said roll, and a part leaving said roll, means for moving said endless screen under tension so as to carry the web upon said web-supporting reach through the saturant in said container toward, in contact with, and away from said roll; said roll being rotated at a speed such as to move the lower portion of the cylindrical surface thereof in the direction and at substantially the speed of movement of the web-supporting surface of said screen; and means for supplying saturant to the upper surface of said web as said web moves away from said roll upon said web-supporting surface of said screen.

2. Apparatus for saturating a wet web of felted fibres in accordance with claim 1, further comprising a doctor blade positioned with respect to said roll so as to act as a scraper, so as to clean off any particles of material tending to adhere to the imperforate cylindrical surface of said roll.

3. Apparatus for saturating a wet web of felted fibres in accordance with claim 1, in which said means for supplying saturant comprises a trough disposed at a level above that of said roll and having walls extending longitudinally substantially parallel to the axis of said roll, and so constructed and arranged that liquid saturant supplied to said trough and flowing over one longitudinally extending wall thereof will be supplied to a pool disposed above the nip where said web moves away from said roll and in contact with the surface of said web which had previously been in contact with said roll.

4. Apparatus for saturating a wet web of felted fibres in accordance with claim 1, in which said means for supplying a saturant comprises a trough disposed at a level above that of said roll and having walls extending longitudinally substantially parallel to the axis of said roll, and so constructed and arranged that liquid saturant supplied to said trough and flowing over one longitudinally extending wall thereof will be supplied to a pool disposed above the nip where said web approaches contact with said roll and in contact with the surface of said web which is to come into contact with said roll.

5. Apparatus for saturating a wet web of felted fibres in accordance with claim 1, in which said means for supplying saturant comprises a trough disposed at a level above that of said roll and having walls extending longitudinally substantially parallel to the axis of said roll, and so constructed and arranged that liquid saturant supplied to said trough and flowing over one longitudinally extending wall thereof will be supplied to a pool disposed above the nip where said web approaches contact with said roll and in contact with the surface of said web which is to come into contact with said roll; and further constructed and arranged so that liquid sautrant flowing over the other longitudinally extending wall thereof will be supplied to a pool disposed above the nip where the web moves away from said roll and in contact with the surface of said web which had previously been in contact with said roll.

6. Apparatus for saturating a wet web of felted fibres in accordance with claim 1, in which said means for supplying saturant comprises a trough disposed at a level above that of said roll and having walls extending longitudinally substantially parallel to the axis of said roll, and so constructed and arranged that liquid saturant supplied to said trough and flowing over one longitudinally extending wall thereof will be supplied to a pool disposed above the nip where said web approaches contact with said roll and in contact with the surface of said web which is to come into contact with said roll; and further constructed and arranged so that liquid saturant flowing over the other longitudinally extending wall thereof will be supplied to a pool disposed above the nip where the web moves away from said roll and in contact with the surface of said web which had previously been in contact with said roll; and further comprising a doctor blade positioned above and in contact with said roll between the pools of saturant so as to act as a scroper with respect to said roll to clean ofi any particles of material tending to adhere to the imperforate surface of said roll, said doctor blade being positioned below and substantially in alignment with said trough.

References Cited in the file of this patent UNITED STATES PATENTS 1,754,024 Keller Apr. 8, 1930 1,939,842 Crumb et al. Dec. 19, 1933 2,049,469 Novak Aug. 4, 1936 2,104,052 Novak Jan. 4, 1938 2,428,113 Grupe Sept. 30, 1947 2,772.603 Waggoner Dec. 4, 1956 

